阅读xtrabackup代码的一点笔记

xtrabackup binary最重要的两个过程是backup和prepare，对应的函数分别是xtrabackup_backup_func()和xtrabackup_prepare_func()，这里做一些阅读代码时的笔记。

xtrabackup backup的线程模型：

1. 一个log拷贝线程；

2. n个ibd文件拷贝线程；

3. 一个io监控线程；

4. 通过suspend_start/suspend_end文件来标注是否启动终止线程；

typedef struct {

datafiles_iter_t *it;

uint num;

uint *count;

os_ib_mutex_t count_mutex;

os_thread_id_t id;

}data_thread_ctxt_t;

数据线程上下文切换工作目录；

116 /** Set if InnoDB must operate in read-only mode. We don't do any

117 recovery and open all tables in RO mode instead of RW mode. We don't

118 sync the max trx id to disk either. */

xb_set_innodb_read_only() 将innodb设成只读模式

srv_backup_mode=TRUE; 将innodb设成backup模式；

设置innodb的一系列参数

innodb_init_param()

xb_normalize_init_values(void)

修改srv_unix_file_flush_method

根据bp大小，调整srv_max_n_threads参数

1017 /*********************************************************************//**

1018 Initializes the synchronization primitives, memory system, and the thread

1019 local storage. */

srv_general_init()

ut_crc32_init()

xb_filters_init()

2567 /************************************************************************

2568 Initializes the I/O and tablespace cache subsystems. */

xb_fil_io_init(void)

838 /******************************************************//**

839 Initializes the log. */

log_init(void)

585 /*********************************************************************//**

586 Creates the lock system at database start. */

lock_sys_create()

open_or_create_log_file

创建xtrabackup_extra_lsndir/extrabackup_traget_dir

表空间memory cache

fil_system_t* f_system = fil_system;

recv_find_max_checkpoint(&max_cp_group, &max_cp_field)

log_group_read_checkpoint_info(max_cp_group, max_cp_field)

checkpoint_lsn_start/checkpoint_no_start

确认一致的checkpoint状态；

创建XB_LOG_FILENAME文件，写入文件头信息；

创建io_watching_thread;

从checkpoint位置开始copy log文件；

xtrabackup_copy_logfile(checkpoint_lsn_start, FALSE)

log_copying/log_copying_stop

创建日志copy线程

os_thread_create(log_copying_thread, NULL, &log_copying_thread_id);

2591 /****************************************************************************

2592 Populates the tablespace memory cache by scanning for and opening data files.

2593 @returns DB_SUCCESS or error code.*/

xb_load_tablespaces()

挂起，等待XB_FN_SUSPENDED_AT_START文件被删除

xtrabackup_suspend

xb_page_bitmap_init()

根据xtrabackup_parallel设置，创建data_copy_thread_func线程

等待所有data_copy_thread_func线程退出

挂起，等待XB_FN_SUSPENDED_AT_END文件被删除

xtrabackup_suspend

读取最新的checkpoint， 记录在metadata的to_lsn字段；

通过设置log_copying=FALSE && set log_copying_stop，停止log_copying_thread；

创建一个文件XB_FN_LOG_COPIED，通知外部脚本，log_copying_thread已经结束；

写metadata；prepare_func

1. 切换到xtrabackup_real_target_dir

2. 读取XTRABACKUP_METADATA_FILENAME，获取原信息；

metadata_type

3. xtrabackup_init_temp_log()

4. innodb_init_param()

2670 /************************************************************************

2671 Initialize the tablespace memory cache and populate it by scanning for and

2672 opening data files.

2673 @returns DB_SUCCESS or error code.*/

xb_data_files_init()

应用增量到全量

xtrabackup_apply_deltas()

重设innodb初始化参数

innodb_init_param()

innodb_init()遍历文件

mtr_start -> mtr_commit

trx_sys_print_mysql_binlog_offset()

将binlog位置信息输出到 xtrabackup_binlog_pos_innodb文件中

xtrabackup_close_temp_log(TRUE)

输出记录metadata_log

backup

$./xtrabackup_56 --defaults-file=/u01/my3928/my.cnf --backup --target_dir=/u01/xianlin.lh/backup_dir/

./xtrabackup_56 version 2.1.8 for MySQL server 5.6.15 Linux (x86_64) (revision id: undefined)

xtrabackup: uses posix_fadvise().

xtrabackup: cd to /u01/my3928/data

xtrabackup: using the following InnoDB configuration:

xtrabackup: innodb_data_home_dir = /u01/my3928/data

xtrabackup: innodb_data_file_path = ibdata1:4G;ibdata2:16M:autoextend

xtrabackup: innodb_log_group_home_dir = /u01/my3928/data

xtrabackup: innodb_log_files_in_group = 4

xtrabackup: innodb_log_file_size = 1073741824

2014-05-05 17:29:35 2ac06bc4a2c0 InnoDB: Using Linux native AIO

xtrabackup: using O_DIRECT

>> log scanned up to (1451746590)

[01] Copying /u01/my3928/data/ibdata1 to /u01/xianlin.lh/backup_dir/ibdata1

>> log scanned up to (1451746590)

>> log scanned up to (1451746590)

>> log scanned up to (1451746590)

>> log scanned up to (1451746590)

>> log scanned up to (1451746590)

>> log scanned up to (1451746590)

>> log scanned up to (1451746590)

>> log scanned up to (1451746590)

>> log scanned up to (1451746590)

>> log scanned up to (1451746590)

>> log scanned up to (1451746590)

>> log scanned up to (1451746590)

>> log scanned up to (1451746590)

>> log scanned up to (1451746590)

>> log scanned up to (1451746590)

>> log scanned up to (1451746590)

>> log scanned up to (1451746590)

>> log scanned up to (1451746590)

[01] ...done

[01] Copying /u01/my3928/data/ibdata2 to /u01/xianlin.lh/backup_dir/ibdata2

[01] ...done

[01] Copying ./test/t2.ibd to /u01/xianlin.lh/backup_dir/test/t2.ibd

[01] ...done

[01] Copying ./test/t4.ibd to /u01/xianlin.lh/backup_dir/test/t4.ibd

[01] ...done

[01] Copying ./test/t3.ibd to /u01/xianlin.lh/backup_dir/test/t3.ibd

[01] ...done

[01] Copying ./test/sbtest1.ibd to /u01/xianlin.lh/backup_dir/test/sbtest1.ibd

>> log scanned up to (1451746590)

>> log scanned up to (1451746590)

[01] ...done

[01] Copying ./test/t1.ibd to /u01/xianlin.lh/backup_dir/test/t1.ibd

[01] ...done

[01] Copying ./mysql/innodb_index_stats.ibd to /u01/xianlin.lh/backup_dir/mysql/innodb_index_stats.ibd

[01] ...done

[01] Copying ./mysql/slave_worker_info.ibd to /u01/xianlin.lh/backup_dir/mysql/slave_worker_info.ibd

[01] ...done

[01] Copying ./mysql/innodb_table_stats.ibd to /u01/xianlin.lh/backup_dir/mysql/innodb_table_stats.ibd

[01] ...done

[01] Copying ./mysql/slave_relay_log_info.ibd to /u01/xianlin.lh/backup_dir/mysql/slave_relay_log_info.ibd

[01] ...done

[01] Copying ./mysql/slave_master_info.ibd to /u01/xianlin.lh/backup_dir/mysql/slave_master_info.ibd

[01] ...done

>> log scanned up to (1451746590)

xtrabackup: The latest check point (for incremental): '1451746590'

xtrabackup: Stopping log copying thread.

.>> log scanned up to (1451746590)

xtrabackup: Transaction log of lsn (1451746590) to (1451746590) was copied.

创建备份的流程

http://www.percona.com/doc/percona-xtrabackup/2.1/xtrabackup_bin/creating_a_backup.html

1 backup_type = full-backuped

2 from_lsn = 0

3 to_lsn = 1451746590

4 last_lsn = 1451746590

5 compact = 0prepare

$./xtrabackup_56 --defaults-file=/u01/my3928/my.cnf --prepare --target-dir=/u01/xianlin.lh/backup_dir/

./xtrabackup_56 version 2.1.8 for MySQL server 5.6.15 Linux (x86_64) (revision id: undefined)

xtrabackup: cd to /u01/xianlin.lh/backup_dir/

xtrabackup: This target seems to be not prepared yet.

xtrabackup: xtrabackup_logfile detected: size=2097152, start_lsn=(1451746590)

xtrabackup: using the following InnoDB configuration for recovery:

xtrabackup: innodb_data_home_dir = ./

xtrabackup: innodb_data_file_path = ibdata1:4G;ibdata2:16M:autoextend

xtrabackup: innodb_log_group_home_dir = ./

xtrabackup: innodb_log_files_in_group = 1

xtrabackup: innodb_log_file_size = 2097152

2014-05-05 18:38:32 2b7f2f5202c0 InnoDB: Using Linux native AIO

xtrabackup: using the following InnoDB configuration for recovery:

xtrabackup: innodb_data_home_dir = ./

xtrabackup: innodb_data_file_path = ibdata1:4G;ibdata2:16M:autoextend

xtrabackup: innodb_log_group_home_dir = ./

xtrabackup: innodb_log_files_in_group = 1

xtrabackup: innodb_log_file_size = 2097152

2014-05-05 18:38:32 2b7f2f5202c0 InnoDB: Using Linux native AIO

xtrabackup: Starting InnoDB instance for recovery.

xtrabackup: Using 104857600 bytes for buffer pool (set by --use-memory parameter)

InnoDB: The InnoDB memory heap is disabled

InnoDB: Mutexes and rw_locks use GCC atomic builtins

InnoDB: Compressed tables use zlib 1.2.3

InnoDB: Using Linux native AIO

InnoDB: Using CPU crc32 instructions

InnoDB: Initializing buffer pool, size = 100.0M

InnoDB: Completed initialization of buffer pool

InnoDB: Highest supported file format is Barracuda.

InnoDB: The log sequence numbers 552524932 and 552524932 in ibdata files do not match the log sequence number 1451746590 in the ib_logfiles!

InnoDB: Database was not shutdown normally!

InnoDB: Starting crash recovery.

InnoDB: Reading tablespace information from the .ibd files...

InnoDB: Restoring possible half-written data pages

InnoDB: from the doublewrite buffer...

InnoDB: Last MySQL binlog file position 0 26767310, file name mysql-bin.000023

InnoDB: 128 rollback segment(s) are active.

InnoDB: Waiting for purge to start

2014-05-05 18:38:33 2b7f49056700 InnoDB: Warning: table 'test/sbtest1'

InnoDB: in InnoDB data dictionary has unknown flags 50.

InnoDB: 5.6.15 started; log sequence number 1451746590

[notice (again)]

If you use binary log and don't use any hack of group commit,

the binary log position seems to be:

InnoDB: Last MySQL binlog file position 0 26767310, file name mysql-bin.000023

xtrabackup: starting shutdown with innodb_fast_shutdown = 1

InnoDB: FTS optimize thread exiting.

InnoDB: Starting shutdown...

InnoDB: Shutdown completed; log sequence number 1451747281

prepare的流程：

http://www.percona.com/doc/percona-xtrabackup/2.1/xtrabackup_bin/preparing_the_backup.html

1 backup_type = full-prepared

2 from_lsn = 0

3 to_lsn = 1451746590

4 last_lsn = 1451746590

5 compact = 0